Puzzled (rounds not chambering)

[SGK]

The burr on the case mouth. I believe it meant the cases were sitting up on this burr and so with a bullet seated there was interference on the bullet. Since the interference was on the bullet, rather than case, it did not show when chambering the same cases without bullets. Shoulder bump, case neck length etc was all fine. The burr was not. Deburr a case, re-seat a bullet at the same CBTO and everything chambered ok. Frank nailed it.

(When I put the cases back through my neck turning lathe some cases had a small amount of brass trimmed right near the case mouth even after deburring.)

Re the video I posted of my chamber I realized later I hadn't cleaned the rifle after shooting the rounds that day. Duh! I received the JB only today and haven't yet put it to use but, having cleaned the rifle thoroughly and looked again in the borescope I don't see any ring. Perhaps I should post another vid for you guys to check or just give it a go over with JB for good measure but rounds are chambering easily without it.

 

[SGK]

One other, unrelated, thing I realized as a result of all this was that any measurement of 'touch', for example using the Wheeler method, has to be done with fully fire-formed and bumped cases, i.e. as they will be shot. I had wondered for some time why an early estimation of CBTO at touch was shorter than a later one I did. I realized while going through all of this that the earlier estimation was using a case that hadn't been fully fire-formed. (I'd just got the rifle and brass.) A lot of the difference between the two estimations could be explained simply by the longer CBTS of the case, 5 thou. It makes me like even more the idea behind the Accuracy One seating depth comparator which measures case shoulder to ogive (CSTO) rather than CBTO.

The biggest lesson is that the tiniest little things can cause a huge amount of frustration

 

[SGK]

Had it been principally a carbon ring then the scuffing on the bullet would have occurred all round it as I tried chambering the round repeatedly. (The bullet would go into the chamber randomly throughout its cross-section dimension spreading the scuff around the bullet.) The fact that the scuff did not spread suggested an issue with the case/bullet and led me back to trying Frank's suggestion.

 

[243winxb]

(When I put the cases back through my neck turning lathe some cases had a small amount of brass trimmed right near the case mouth even after deburring.)

A burr forms on the case mouth when trimming brass to length. Two things can make the burr excessive.
Feed rate to high and/or a dull cutter head.

On a Lyman steel cutter, a tooth brush with some Break Free CLP every 2nd or third case helps. Lubes and removes brass trimmings.

A carbide cutter may worth the extra cost?

 

[SGK]

Wasn't from trimming to length. This go around next to none needed trimming. Had they needed trimming, the burr would have been trimmed off. Most likely from tumbling brass and not de-burring properly afterwards.

 

[bozo699]

The burr on the case mouth. I believe it meant the cases were sitting up on this burr and so with a bullet seated there was interference on the bullet. Since the interference was on the bullet, rather than case, it did not show when chambering the same cases without bullets. Shoulder bump, case neck length etc was all fine. The burr was not. Deburr a case, re-seat a bullet at the same CBTO and everything chambered ok. Frank nailed it.

(When I put the cases back through my neck turning lathe some cases had a small amount of brass trimmed right near the case mouth even after deburring.)

Re the video I posted of my chamber I realized later I hadn't cleaned the rifle after shooting the rounds that day. Duh! I received the JB only today and haven't yet put it to use but, having cleaned the rifle thoroughly and looked again in the borescope I don't see any ring. Perhaps I should post another vid for you guys to check or just give it a go over with JB for good measure but rounds are chambering easily without it.

That’s above awesome!…. Glad your back up and shooting!.. if it were me and your scoping showed the ring gone I wouldn’t try to remove something that wasn’t there!… every time we put a cleaning rod in our rifle we chance screwing something up
Wayne

 

[Webster]

I think must be differences in bullet curvature between above where my Forster Datum Dial kit measures. On the bottom two rounds below you can see where the lands have scuffed the bullet. My datum Dial Kit measure a few mm below this point. You can see where the Datum Dial has marked the bullet versus the scuff.


View attachment 1343999

Why is there a deep groove at the neck/shoulder junction. Bottom photo, does the shiny area on the bullet have anything to do with the matching rub mark on the neck?

 

[SGK]

See posts 72 onwards. I'm not sure where this is coming from. I will need to keep an eye on it. There's no groove there after turning again and passing the cases through my sizing die. I would speculate however that it comes from sizing with brass flowing forward on firing, pushed back at the shoulder with a shoulder bump and pushed towards the neck/shoulder junction by the bushing. But I don't know. I need to fire this newly turned brass and see when/if it appears again.

The mark was on all my brass even that which chambered without interference at the bullet and removing the burr at the mouth allowed all that didn't chamber previously to chamber easily (prior to doing any neck turning again).

Here's a more typical result from the neck turning again (the first one I did took off too much brass by about 2/10ths of a thou) showing how brass was removed from the lower part of the neck and shoulder junction (and the occasional tiny bit of residual burr at the mouth). Versus the prior pic, this example and all cases have had an expander mandrel through the case mouth to prepare for turning, neck turned, resized to tighten neck, expander mandrel for 1 thou tension and primer, powder and bullet seated. No groove so firing is some part of the equation.

 

[SGK]

I went ahead and tried to make another clip from my borescope. I find it difficult to discern things due to the glare of the light and difficulty focusing but I don't see a troublesome carbon ring. Perhaps I am wrong?

 

[bozo699]

I went ahead and tried to make another clip from my borescope. I find it difficult to discern things due to the glare of the light and difficulty focusing but I don't see a troublesome carbon ring. Perhaps I am wrong?

Looks like you got most of it out compared to your first video are you still having problems?
Wayne

 

[SGK]

Ok great. Haven't been back to the range (been down with bronchitis) but have been pottering around at home and thought I'd check this. Latest loaded rounds chamber easily. Haven't been able to see if I can shoot them any better.

 

[M14AMU]

Reduce your bullet depth...seat deeper and the rounds will chamber!

 

[SGK]

Seating depth was not the issue @M14AMU. The issue and solution was covered in posts 59 and 63 etc.

 

[Scalloper]

At 20 thou deeper I'm getting an easier bolt close. Also, you can now see better the scuffing on the bullet, always in the same area butt spreading further back as I seat deeper. It puzzles me that as I have randomly placed the cartridge in the action why the scuffing isn't forming all around the bullet...

View attachment 1344052

It looks to me like its rubbing hard on the feed ramp during chambering.